如何在iOS编程中向视频文件添加和检索自定义元数据？

Question

我正在尝试使用与我的应用相关的自定义元数据保存视频,并在用户从库中选择该视频时尝试检索该视频.我不确定我是否正在保存元数据,因为当我尝试检索元数据时,我无法看到任何内容.我也不确定我是否正确检索元数据.我是iOS新手,感谢任何帮助.我搜索了许多线程和开发人员库,但无法使其工作.

我正在尝试在recordingDidFinishToOutputFileURL委托函数中保存元数据.视频已保存在库中.

NSMutableArray *metadata = [NSMutableArray array];
    AVMutableMetadataItem *mi = [AVMutableMetadataItem metadataItem];
    mi.key = AVMetadataCommonKeyTitle;
    mi.keySpace = AVMetadataKeySpaceCommon;
    mi.value = @"title";
    [metadata addObject:mi];

    NSLog(@"Output saving:%@",outputFileURL);
    AVAsset *video = [AVAsset assetWithURL:outputFileURL];
    AVAssetExportSession *exportSession = [AVAssetExportSession      exportSessionWithAsset:video presetName:AVAssetExportPresetPassthrough];
    exportSession.shouldOptimizeForNetworkUse = YES;
    exportSession.outputFileType = AVFileTypeMPEG4;
    exportSession.metadata = metadata;
    exportSession.outputURL = outputFileURL;
    [exportSession exportAsynchronouslyWithCompletionHandler:^{
        NSLog(@"done processing video!");
        UISaveVideoAtPathToSavedPhotosAlbum(outputFileURL.path, self, @selector(video:didFinishSavingWithError: contextInfo:), nil); 
    }];

我试图在didFinishPickingMediaWithInfo委托函数中检索视频以检查元数据但是无法在completionhandler函数中看到任何内容

        if ([mediaType isEqualToString:(NSString *)kUTTypeMovie]) {
        video_selected = TRUE;
        NSURL *videoURL = [info objectForKey:UIImagePickerControllerMediaURL];

        NSLog(@"video has %@", videoURL.path);
        AVAsset *videoAsset = [AVAsset assetWithURL:videoURL];
        NSLog(@"Loading metadata...");
        NSArray *keys = [[NSArray alloc] initWithObjects:@"commonMetadata", nil];
        NSMutableArray *metadata = [[NSMutableArray alloc] init];
        [videoAsset loadValuesAsynchronouslyForKeys:keys completionHandler:^{

            [metadata removeAllObjects];
            for (NSString *format in [videoAsset availableMetadataFormats])
            {
                [metadata addObjectsFromArray:[videoAsset metadataForFormat:format]];
                NSLog(@"Printing metadata-%@",metadata);
            }


        }];

Answer 1

检查你的错误。您要导出到文件已存在的位置，因此它会导出到自身，这是行不通的。只需导出到不同的位置即可